Microbial Secondary Metabolites and Knowledge on Inhalation Effects

Abstract

Microbial secondary metabolites include compounds produced during the growth of both fungi and bacteria. These compounds are present in workplaces and indoor environments, although the concentrations of single toxins in the air are typically low. Inhalation is considered to be the most significant route of exposure for microbial secondary metabolites in indoor environments although exposure to microbial toxins may happen also via alimentary or dermal route. Inhalation effects of microbial secondary metabolites have been studied experimentally in vivo in animal models, mainly in rodents. In vitro studies with cells of respiratory system and ex vivo cultured tissues have elucidated the mechanisms of action for the most common toxins. However, there are only few epidemiological studies on health effects of mycotoxin exposure, and often the studies are limited by exposure assessment based on single compounds or surrogates of mycotoxin exposure. We summarize here studies on the inhalation effects of microbial toxins showing a wide variety of adverse health effects which are not limited to the respiratory system, and identify the knowledge gaps where future research efforts should be targeted.